Upgraded to Virtual Box 4.2.0. After several days the number of network connections as reported by conntrack -S continually increased to the maximum limit of the machine (65536). Normally the host machine would have a stable "conntrack -S" count of somewhere around 500-600 connections, even after running for months.

Tried combinations of Virtual Box 4.2.0, 4.2.2 and 4.2.4 with kernel-PAE-3.2.3-2.fc16.i686, kernel-PAE-3.4.11-1.fc16.i686 and kernel-PAE-3.6.2-1.fc16.i686. Any combination with 4.2.x resulted in the network connection leak.

Change History

The graphic attached shows 3 distinct periods of network connection leaks. The large flat part of the graph with approx 20k connections was with virtualbox 4.2.x running but no virtual machines running. The flat period after the third peak is with reverting back to Virtualbox 4.1.8.

Reinstalled VirtualBox-4.2-4.2.4_81684_fedora16-1.i686.rpm on kernel 3.4.11-1.fc16.i686.PAE.
Started up a single Guest (Win XP SP3) and even after 10 mins can see an increase in network connection leakage.

Here's a table of conntrack info:

conntrack -L

conntrack -S

Guest Uptime (mins)

Guest Related Conns

505

505

0

660

671

2

749

790

10

138

573

638

20

109

657

812

50

197

493

1129

195

158

523

1423

285

151

100% of the 100 or so guest related connections listed in conntrack -L are for connections back to the hosting machine that provides services to the guest eg web server, squid, SMB etc

One characteristic of this bug is that the connection totals reported by conntrack -L and the totals reported by conntrack -S diverge significantly over time, where those reported by conntrack -L stays around the several hundred mark but those reported by conntrack -S just keeps generally increasing as per attached graph. So looking at connections in conntrack -L shows normal behaviour.

Other information:

Leaks occur with or without Guest Additions running

When the virtual guest stops and is not running then the connection leak also stops.

Also leaks when running Fedora 16 as a guest

Leaks whether guest is active on the network or not. eg WinXP guest has hundreds of conntrack -L entries. Fedora guest has 1 or 2 conntrack -L entries. Leak rate is the same regardless.